Composites are made from two or more materials that remain separate and distinct on a macroscopic level while forming single-body components. Matrix materials and reinforcement materials are two main components of the composites. The reinforcement materials may be stronger and stiffer than the matrix materials and may impart special physical (mechanical and electrical) properties to enhance properties of the matrix materials. In a typical composite structure, a matrix material surrounds and supports reinforcement structures by maintaining relative positions of these structures. The synergetic effect of this combination produces material properties that are superior to that of the matrix and/or reinforcement.
Ceramic matrix composites (CMCs) are specific types of composites that include ceramic matrix materials and, in some instances, ceramic reinforcement materials. Structures formed from CMCs have relatively high mechanical strengths that are often retained at high temperatures. This type of composite materials may be designed to withstand physically demanding conditions, such as high temperatures, oxidation, and the like often associate with aerospace applications.
Some commonly used CMC materials include glass CMCs, organo-metallic CMCs, and non-oxide CMCs. However, these CMC materials are not applicable for many aerospace applications, such as shielding radomes. For example, organo-metallic ceramics have high dielectric constants and are susceptible to oxidation. Non-oxide CMCs often begin to crack at typically about 10 ksi. Other CMC materials change their properties with temperature fluctuations. Furthermore, many CMC materials do not provide hermetically sealing often needed to maintain particular environments, such inside compartments of radomes.